Ore concentration by flotation



Patented Feb. 7, v1939 ORE CONCENTRATION BY FLOTATION John Ross Tuttle,Summit, N. J., assignorto General Chemical Company, New` York, N. Y., acorporation of New York Application September 29, 1937, Serial No.166,303

8 Claims.

This invention relates to notation or mineral collecting agents and tothe separation of minerals and the concentration of ores by flotationprocesses. The invention is more particularly directed to flotation ormineral collecting agents comprising 'sulfur bearing oils derived fromsludges formed in oil refining processes in which sulfuric acid isemployed, and is also particularly directed to processes forvseparationof minerals and concentration of ores carried out with the utilizationof such sulfur bearing voils as 4flotation or mineral collectingagents..

The principal objects of the invention are'directed to improvements inthe separation of minerals and the concentration of `ores by flotationprocesses and to the provision of sulfur bearing oils for this purpose.lIt is a further aim of the invention to provide sulfur bearing notationor lmineral collecting oils having a relatively high sulfur contentsubstantialy all of which sulfur is in strong chemical combination. Itis a iuras sulfur dioxide, carbon dioxide, nitrogen and uncondensablehydrocarbons. Y

According to the present invention, it has been discovered that whensludge material, resulting from` treatment with.sulfuric acid ofrelatively light hydrocarbon oil distillates containing substantialquantities of sulfur compounds, is dissociated preferably by destructivedecomposition by heating to form a hot gas mixture containinghydrocarbon vapors and the gas mixture is cooled, for example to aboutnormal temperature, an oily condensate is obtained which is a sulfurbearing oil possessing properties rendering the oil esspecially suitedforuse as otation or mineral collecting agents in the separation ofminerals and the concentration of ores by notation processes. The oilsso produced are light colored, light bodied, stable oils, high in sulfurin strong chemical combination, and do not become turbid or deposit freesulfur on standing. y

A further appreciation of the objects and advantages of the inventionmay be had from a consideration of thel following description oi theoils constituting the improved notation or mineral collecting agents, offlotation processes involving 1 utilization of the improved notation ormineral collecting agents, and of methods for making the improvedflotation ,or mineral .collecting agents. They accompanying drawingillustrates diagrammatically apparatus by which the improved otation ormineral collecting oils may be made.

Referring to the drawing, I indicates the combustion chamber of afurnace adapted to burn coal, coke, oil, natural gas or other fuel.Mounted in chamber I0 is a decomposing kiln or retort II of anydesirable construction, for lexample a xed shell provided with suitablemechanism such as a screw conveyor, not shown, to facilitate dischargeof coke. A rotary retort may also be employed if desired. Preferably anexternally heated'kiln adapted to substantially exclude admission of airis used. One end of kiln II communicates with a gas outlet I3, and theopposite end projects into a header I4 into which the solid residue ofthe decomposition of the acid sludge is continuously discharged. HeaderI4 empties into air-lock I through which coke may be discharged withoutadmitting air to the kiln. Acid sludges, constituting sources of theflotation or mineral collecting oils of the invention, are run into thekiln from supply tank I1 through a valve-con-Y trolled pipe I8. Gas,outlet I3 is connected to the lower end of a cooler or condenser 20 ofany suitable construction, either air or water cooled, and operated soas to reduce the temperature of the gas stream to substantiallyatmospheric to condense the bulk of the water vapor and a major portionof condensable hydrocarbons contained in the gas. Condensate from thecooler drains into a separator or collecting tank 2I throughl apipe 22having a liquid seal.

Thevgases uncondensed in cooler 20, containing principally sulfurdioxide, are discharged through gas line 23, and may be` used asdesired, for example in the manufacture of sulfuric acid by the contactprocess.

Separator 2l may be a tank or vat large enough to permit continuousgravity separation of water and oil 'contained in the condensatedischarged from condenser 20. The sulfur bearing hydrocarbon oils of thecondensate rise to the top of the mass in the separator, and may bewithdrawn continuously or intermittently through pipe 25 discharginginto a collecting tank 2,6. Water settling to the bottom of theseparator may be drawn off 'through pipe 21, controlled by valve 28,

and discharged to Waste or otherwise disposed of.

The still 30, of any approved construction, may be externally heated byhot combustion gases generated in brickwork setting 3|. Raw condensatefrom collecting tank 26 is run into the still through pipe 38,controlled by valve 39. Vapors generated in the still flow through line4I to a condenser 43, the condensate of which drains through pipes 45and 46, into receivers 50 and 5I.

The improved notation oilsof the invention may be made in apparatus suchas illustrated in the drawing and described above by operatingsubstantially as follows.

In producing the improved flotation or mineral collecting agents, acidsludges which may be employed are those resulting from sulfuric acidtreatment of light distillate oils obtained from petroleum crudescontaining sulfur. The .acid sludges employed in making theflotation ormineral collecting oils ofthe present invention are preferably sludgesresulting from treatment with sulfuric acid of light hydrocarbon oildistillates such as gasoline and kerosene, containing not less thanabout 0.15% sulfur, although distillates containing less sulfur may beemployed if desired. Illustrative examplesof distillate oils from whichsludges are produced of a character suitable' for use in the presentinvention are straight-run gasoline distillates containing about 0.15%sulfur or more, and cracked distillate averaging 0.25 to 0.30% sulfur ormore.

Sludge material of the type indicated and which may have for example atitratable acidity of 40% to 60% expressed as HzSO4 is Acontinuously fedinto kiln Il from supply tank i1. 'l'.'he burners in furnace Il) areadjusted to maintain within the kiln 'tempertures desirably not inexcess of about 750 F., as above this temperature thev sulfur oilsconstituting the notation or mineral collecting agents of the presentinvention tend to be decomposed. The preferred temperatures are about`250. F. at the sludge inlet end, and about 500 F. to 600 F. at the cokeoutlet end of thekiln.

The sludge, gradually passed through the retort, is relatively graduallyheated through the preferred temperature range and is decomposed by theaction of heat,-and the free and/or combined sulfuric acid of the sludgeis reduced to sulfur dioxide by the hydrogen of the hydrocarbons and/orby the carbonaceous matter contained in the sludge. The sludge materialis thus dissociated, as by the destructive distillation methodindicated, with production of water vapor, and hydrocarbon vapors andsulfur compounds are formed. Residual coke is continuously dischargedfrom the kiln through air-lock I5.. The major part of the flotation ormineral collecting oils of theinvention appears to have been evolved bythe time the sludge has reached a temperature drocarbon gases and watervapor.

'Ihe gas resulting from the decomposition of the sludge containsprincipally water vapor and sulfur dioxide, substantial amounts ofcondensable hydrocarbons vand sulfur compounds and smaller quantities ofuncondensable hydrocarbons and gases such' as carbon dioxide, carbonmonoxide, and nitrogen. For example, one representative sludge having atitratable acidity of about 50% expressed as H2SO4 yielded ondecomposition by destructive distillation about 28% residual coke and aretort gas which after cooling to about normal temperatures, producedabout 6%v condensable oils, about 35% water, based on the weight of thesludge, the balance of the retort gas comprising sulfur dioxide, carbondioxide, l

carbon monoxide, nitrogen, uncondensable hy- As previously noted,according to the preferred way for making the sulfur bearing oils' ofthe invention, decomposition of sludges is effected in the kilnsubstantially in the absence of oxygen and in the absence ofotherextraneous gases. When so operating. the volume of gas formed islessened an -loss of oil by volatilization is decreased.

The hot gaseous and vaporous products of decomposition of the sludge aredischarged from the kiln and passed through conduit I3 into condenser 20in which the gases are cooled to substantially normal temperatures.Cooling may be accomplished by circulating through the condenser inindirect heat exchange relation with the retort gas mixture any suitablecooling liquid about normal atmospheric temperatures.

During cooling of the retort gas mixture in the condenser 20,substantially all of the water vapor and the major portion of thecondensable hydrocarbon vapors and sulfur compounds are condensed out ofthe gas stream. The "condensate of cooler 20, containingvaryingproportions of water and liquid hydrocarbons'and sulfur compounds, isdrained through pipe 22 into separator 2|. In the latter, the oils riseto the top of the liquid mass inthe tank, and'may be intermittently orcontinuously withdrawn through pipe 25 into tank 26 for collecting whatmay be termed a raw condensate or initial sulfur oil. The water settlingto the bottom of the separator 2| may be discharged from the systemthrough pipe 21.

The oil collecting 'in tank 26 is an 'oil containing generally fromabout 3 to about 22% sulfur, apparently in strong chemical combination'.It will be understood the sulfur content of this condensate may varyconsiderably in accordance with the characteristics of the initial crudeoils and of the acid sludges produced on treatment of the hydrocarbonoil distillates with sulfuric acid. For example, an acid sludge formedthrough sulfurie acid treatment of -a straight-run gasoline yielded anoil condensate of 12% by volume of the sludge, the `condensate analyzing14.8% sulfur. A cracked distillate sludge yielded by Volume of oilcondensate having a sulfur content of 7.5%. AIn another instance, acracked distillate averaging about .25 to .30% sulfur produced ontreatment with sulfuric acid a sludge which, on treatment in accordancewith the present method,

yielded 10.8% by volume of oil condensate analyt-v ing 20.8% sulfur.

According to the invention, it has been found Ithat oils produced aresulfur bearing oils havemployed directly as flotation or mineralcollecting agents in notation processes. However, the oil in this statecontains appreciable quantities of foreign matter, such as coke dust andtars,

which under some circumstances may be desirably removed. Further,v theoil collecting in tank 26 comprises several low and high boilingfractions.- The raw condensate of tank 26, the raw condensate of tank 26with foreign matter such as' coke dust and tars removed, a lightfraction of the raw condensate or a heavy fraction of the raw condensatemay be suited for flotation of different y marked action as flotation ormineral collecting agents in ore concentration, in general theyexhibitinsulcient frothing qualities and thereforel may be employed to bestadvantage in conjunction With any suitable or well-known frothing agent,e. g. pine oil, cresylic acid, coal tar acids, terpineol, turpentine,etc.4 They may be also sometimes used to advantage in conjunction withother flotation agents. y

lThe process of the present invention can be carried out in any suitableapparatus, for example, those of the pneumatic type such as the Mc-Intosh cell, or those where the air is incorporated with the pulp byagitation, such as the Fahrenwald or Denver apparatus, or the like.

It is of advantage in some cases, as with certain copper ores, tosubject the ore pulp to the action of an amount of alkali sufficient togive it an alkaline reaction before subjecting it to flotation with theaid of the flotation agents of the present invention. The alkaliA may becaustic `alkali such as caustic soda, or an alkaline salt such as sodaash, or it may be calcium oxide or hydrate. The flotation 'agents may beadded to the ball or equivalent mill during grinding of the ore, to theconditioner, or to the flotation cell.

In the differential separation of various minerals, such as zinc blendefrom associated minv erals, the presence of an alkali metal cyanide, orof copper sulfate or other salts, is sometimes advanta'geous. y

'I'he amount of flotation or mineral collecting oils required to be usedin any given flotation process will vary, depending partly on thecharacter and composition of the ore, partly on the character of thesludge material from which the oils are derived, and partly on otherconditions encountered in practice.

This invention may be illustrated by the following speciflc examples:

Example 1 Oil A .08# per net ton of ore treated Ore subjected topreferentiall flotation in mechanical machines to recover Pb and Zn. TheWater used in the entire operation, i. e. in grinding and in flotation,was new water, i. e. water that did not contain flotation agentspreviously used in the flotation process. Reagents used to float Pb andZn-A Lead float Zinc float Cresylic acid.- .10# Oil A .20# Pine oi1,.--`.04# C11SO4.5H2O 2.0 Oil A.l .04# Na 2CO3 3.0

Pine oil .04# pH 8.7 9.2 l Temp--. 19 C. 19 C.

` Rougher cells Pb Zn Fc Percent Percent Percent Heads contained--. 4.09.' 4.1 Pb conc. contained. 63.8

Zn conc. contained.. l. 0 Tails contained 0.05

^ Pb conc. contained 72.

' Example 2 Flotation oil used: Oil'B-composite oil collected as asingle fraction from condenser 43 and stabilized with 20% NaOH solutionand 30% HzSOi as described.

lOre used: a lead-zinc-iron-sulde ore containing Pb 4.7%, Zn 7.75%, Fe3.44%. Ore initially ground in ball mill with following reagents:

vOil B 0.104# per net ton of ore treated NacN .3o ZnSO4.7I-I2O 1.0 #1

Ore subjected to preferential flotation in mechanical machines torecover Pb and Zn. New water was used in the entire operation. Reagentsused to float Pb and Zn- Lead float Zinc float Cresylic acid--- .10 #atOil B .21# Pine oil .02 #1 CuSO4.5H2O 2.0 #r Oil B .022# NazCO: 3.0 fPine oil .04#

pH v8.9 Temp 18 C.

Percent Percent 4. 7 7. 75

Heads contained 3 Zn conc. contained 2.8 u Tails contained 0.03

Overall recovery of total Pb and Zn of initial ore- Lead- 91.2% in Pbconc. 8.3% in Zn conc. 0.50% in tails Zinc- 1.6% in Pb conc. 93.6% in Znconc. 4.8% in tails.

I claim:

1. The improvement in the concentration of minerals by flotation whichcomprises subjecting mineral in the form of a pulp to a froth flotationoperation in the presence of a relatvely lightbodied, light-colored, lowviscosity sulfur oil boiling at temperatures less than about 650 F.,stable with respect to. sulfur deposition, substantially free of freesulfur, containing alkyl sulfldes, having a sulfur content not less thanabout 3% and formed by dissociating sludge material, resulting fromsulfuric acid treatment of hydrocarbon oils obtained from sulfurcontaining crudes, with aid of vheat at temperatures not more thanvabout 750 F. to break up the sludge under conditions to form a hot gasmixture containing sulfur bearing oil vapors, and cooling the gasmixture to form an oily condensate boiling at temperatures less thanabout 650,F.

2. The improvement in the concentration of minerals'by flotation whichcomprises subjecting mineral in the form of a pulp to a froth flotationoperation in the presence of a relatively lighttillation operation maybe carried out in any suitable still, preferably one provided withequipment for collecting separate fractions of distillate. From theabove, it will be understood distillation of the raw condensate isprincipally for two purposes, first, to remove coke and tars from theoil, and second, to produce preferably two fractions, one having arelatively low boiling range, and another fraction having a higherboiling point range. Distillation may be effected for example byexternal heating of still 30.. If desired, distillation of the crudecondensate may also be accomplished at temperatures lower than thosehereinafter mentionedby introducing live steam directly into the oilbody while externally heating the same. Distillation may also beeffectedfthough possibly less desirably, by super-V heated live steam,using steam'at slightly above atmospheric pressurev and heated to say225250 F. before introduction into the oil. Vacuum distillation may beemployed if desired.

Still maybe operated to produce a first cut including all the oilsdistilling over at temperatures up to about 350 F. at normal pressure.Vapors. generated within this temperature range are liqueed invcondenser 43, and are run into receiver 50. This relatively low boilingfraction may for example constitute approximately 20% by weight of theraw condensate fed into still 30. When removal of these low boilingfractions from the oil in still 30 is substantially complete, thetemperature is raised to distill over oils having boiling points ranginglfrom about 350 F. up to about 650 F. Vapors formed are condensed incooler43, and may be recovered in receiver 5I. This high boilingfraction may comprise for eX- ample (iO-66% by weight of the rawcondensate introduced into still 30. Approximately 10% by weightof theoriginal raw condensate withdrawn from tank 26 may remain as a coke orasphalt residue in the still, and around 5-10 by weight of theoriginalraw condensate may be lost inthe distillation operation asuncondensable .vapors and gases. The low boiling cut recoveredl inreceiver` 50 contains a slightly higher percentagel of sulfur than thehigher boiling fraction collected in receiver 5i. If desired, all of thevapors evolved in still 30 may be condensed and` collected in a singlereceiver instead of in two receivers as 50 and 5|. .In this situation,while there is some decomposition with liberation of H28, .thecondensate collected corresponds in a general way with the condensatecollected in tank` 26 except that foreign matter, such as coke-dust andtars, have been removed.

Any of the foregoing oils may be used as flotation or mineral collectingagents, directly as collected in tank 26 or as collected as a singlefrac-` tion from condenser 43, or as collected in re- Aceivers 50 or 5|.The oils, however, apparently contain substances .such as pyridines andmer captans which impart to the oils undesirable odors and which tend torender the oils somewhat unstable on standing. Accordingly, itispreferred to further treat the oils to stabilize the same and removeodors. 'This may be accomplished by treating the oils with a solution ofcaustic soda or sulfuric acid or both. When-l employing caustic alkali,as is preferred, the oil may be agitated with a 20% caustic sodasolution at temperatures of about 190 F. untilreaction appears complete.The reaction products are allowed to settle, and are withdrawn. The oilmay then be washed with water to remove traces 'of alkali, andbrightenedas by blowing with air.

The oils may also be stabilized by treating with sulfuric acid, sayabout equal volume, and washed with water and alkali to remove traces ofacid.l It is preferred to use acid of concentration not in excess ofabout 60% H2SO4, since acid of this or less'concentration does notappear to ment with both caustic alkali and sulfuric acid.

In this case, after subjecting the oils to the caustic soda treatmentnoted above, and removing the alkali extract; the oils are washed withWater to remove the alkali, and then treated with one or more washes ofequalvolume of dilute sulfuric acid, for example 30% HnSOi. The nal oilproducts may be washed with water to remove traces of acid, and thenbrightened by blowing -With air, or other methods.

In the case where the foreign matter is removed from the condensate oftank 26, as by distillation and collection of all the distillate in asingle receiver, the resulting oil may be stabilized asf described.

The oils stabilized, for example as mentioned labove are sulfur bearingmineral oils, light bodied, possessing a characteristic odor, and have ahigh sulfur content, substantially all of which is in strong chemicalcombination. It appears substantial amounts of the contained sulfur Aispresent as alkyl sulfldes and possibly also some disuldes, and othersulfur bearing compounds. The sulfur contentvaries from about 3 to about.22%. The oils on standing do not become turbid or deposit sulfur. Theoils of the invention are a light straw color. The specic gravity of arepresentative oil is about 0.98. 'I'he viscosity is low, about 32 to35i `Saybolt at 100 F.-

Instead of decomposing the acid sludge by heating as described inconnection with the drawing, the original acid sludge may be subjectedto hydrolysis as by steaming with live steam, for say an hour, untilseparation of weak acid (sludge acid) and an upper acid tar layer takesplace. The weak acid may be drawn oi and the resulting acid tar orsludge material decomposed by heating as in a retort Il. The oilydistillate may be taken in two or' more cuts if desired, although it ispreferred tocollect the oily distillate as in tank 261 During steamingof the acid'sludge a light colored distillate may be recovered in asuitable condenser. This distillate andthe condensate collected in tank26 m'ay be separately treated as already described to produce highsulfur oils,

or may be combined and then so treated.

In accordance with the invention, the sulfur bearing oils described,comprising the raw condensate of tank 26, the raw condensate of tank l26distilled toremove foreign matter such as tars and coke, or either ofthe fractions recovered in receivers 50 and 5I, may be used instabilized or unstabilized condition as flotation or mineral collectingagents, for the separation of minerals or 'the concentration of oresbyflotation processes carried out generally in accordance with thev knownpractices. While the agents ofthe present invention show" of heat attemperatures not more than about 750 F. to break upthe sludge underconditions to form a hot gas mixture containing water and sulfur bearingoil vapors, cooling the gas mixture to form a condensate comprisingWater and oil, separating Water from oil, distilling the oil, andrecovering as condensate oil boiling at temperatures less than about 650F.

3. The improvement in the concentration of 4minerals by notation whichcomprises subjecting mineral in the form of a pulp to a froth flotationyoperation in the presence of a relatively lightbodied, light-colored,low viscosity sulfur oil boiling at temperatures less` than about 650F., stable with respect to sulfur deposition, substantially free of freesulfur, containing alkyl suldes, having a sulfur content not less thanabout 3% and formed by dissociating sludge material, resulting fromsulfuric acid treatment of hydrocarbon oils obtained from sulfurcontaining crudes, with aid of heat at temperatures not more than about750 F. to break up the sludge under conditions to form a hot gas mixturecontaining Water and sulfur bearing oil vapors, cooling the gas mixtureto form a condensate comprising Water and oil, separating Water fromoil, distilling the oil, recovering as condensate oil boiling attemperatures less than l about 650 F., and stabilizing the oil.

4. The' improvement in the concentration of l minerals by flotationwhich comprises subjecting mineral in the form of a-pulp to a frothflotation operation in the presence of a relatively lightbodied,light-colored, low viscosity sulfur oil boiling at temperatures lessthan about 650 F., stable with respect to sulfur deposition,substantially free of free sulfur, containing alkyl sulfides, having asulfur content not less than about 3% and l formed by dlssociatingsludge material, resulting from sulfuric acid treatment of hydrocarbon`distillate oils containing not less than about 0.15% sulfur, with aid ofheat at temperatures not more than about 750 F. to break up the sludgeunder conditions to form a hot gas mixture containing sulfur bearing oilvapors, and cooling the gas mixture to form an oily condensate boilingat temper- 'atures less than about 650 F.

5. The improvement in the concentration of minerals by flotation whichcomprises subjecting l mineral in the form of a pulp to a froth notationthan about '750 F. to break up the sludge under conditions to form a hotgas mixture containing water andsulfur bearing oil vapors, cooling thegas mixture to form a condensate comprising Water and oil, separatingWater from oil, distilling the oil, and recovering as condensate oilboiling at temperatures less than about 650 F.

6. The improvement in the concentration of minerals by notation whichcomprises subjecting mineral in the form of a pulp to a froth flotationoperation in the presence of a relatively lightbodied, light-colored,low viscosity sulfur oil boiling at temperatures less than about 650 F.,stable with respect to sulfur deposition, substantially free of freesulfur, containing alkyl suldes, having a sulfur content not less thanabout 3% and formed by dissociating sludge material, resulting fromsulfuric acid treatment of hydrocarbon distillate oils containing notless than about 0.15% sulfur, with aid of heat at temperatures not morethan about '750 F. to break up the sludge under conditions to form a hotgas mixture containing water and sulfur bearing oil vapors, cooling thegas 'mixture to form a condensate comprising Water and oil, separatingwater from oil, distilling the oil, recovering as condensate oil boilingat temperatures less than about 650 F., and treating the oil withcaustic alkali to stabilize the same.

7. 'Ihe improvement in the concentration of minerals by notation whichcomprises subjecting mineral in theform of a pulp to a froth flotationoperation in the presence of a relatively lightbodied, light-colored,low visc-osity sulfur oil boiling at temperatures not more than about350 F., stable with respect to sulfur deposition, sub-stantially free offree sulfur, containing alkyl suldes, having a sulfur content no lessthan about 3% and formed by dissoclating sludge material, resultingfr-om sulfuric acid treatment of hydrocarbon distillate oils obtainedfrom sulfur containing crudes, with aid of heat at temperatures not morethan about 750 F. to break up the sludge under conditions to form a hotgas mixture containing Water and sulfur bearing oil vapors, cooling thegas mixture to form a condensate comprising water and oil, separatingwater from oil, distilling the oil, and recovering as condensate afraction boiling at temperatures not more than about 350 F.

8. The improvement in the concentration of minerals by flotation whichcomprises subjecting mineral in the form of a pulp to a froth notationoperation in the presence of a relatively lightbodied, light-colored,low viscosity sulfur oil boiling substantially within the range 350 F.to 650 F., stable with respect to sulfur deposition, substantially freeof free sulfur, containing alkyl sulfides, having a su-lfur content notless than about 3% and formed by dissociating sludge material, resultingfrom sulfuric acid treatment of hydrocarbon distillate oils obtainedfrom sulfur containing crudes, with aid of heat attempera-` tures notmore than about 750 F. to break up the sludge under conditions to form ahot gas mixture containing water and sulfur .bearing oil vapors, coolingthe gas mixture to form a condensate comprising water and oil,separating Water from oil, distilling the oil, and recovering ascondensate a fractionl boiling substantially Within the range 350 F. to650 F.

JOHN ROSS TUITLE.

